Thermostat



F. KUHN ET AL Nov. 29, 1932.

THERMOSTAT Filed Feb. l5, 1928 Patented Nov. 29, 1932 UNITED STATES PATENT OFFICE FRANK KUHN AND LAURENCE H. THOMAS, OF DETROIT, MICHIGAN, ASSIGNORS TO AMERICAN ELECTRICAL HEATER COMPANY, OF DETROIT, MICHIGAN, A CORPORA- TION OF MICHIGAN THERMOSTAT Application led February 13, 1928. Serial No. 254,104.

rI his invention relates generally to automatic controls for electrical heating means, and refers more particularly to thermostats for controlling the action of electrical heating units.

In the accompanying drawing:

Figure 1 is a side elevation of a thermostat embodying my invention applied to a melting pot;

Figure 2 is a side elevation of the thermostat;

Figure 3 is a rear elevation of the thermostat with the cover plate removed;

Figure 4 is an end elevation of the thermostat;

Figure 5 is a cross sectional view taken on the line 55 of Figure 2,;

Figure 6 is a longitudinal sectional view taken on the line 6 6 of Figure 2.

Referring now to the drawing, 1 is an attaching plate, 2 and 3 respectively are electrical conductor bars, 4 is a cover plate and 5 is an adjusting device of a thermostat embodying our invention. As shown, this thermostat is mounted upon one side of an aluminum melting pot 6 and is in circuit with a suitable electrical unit 7 on the bottom of the pot. However, it is to be clearly understood that our thermostat may be used adjacent to or upon any device or article to be heated and may be used in conjunction with any form of electrical heating unit.

Preferably the attaching plate 1 is flat and is secured at its longitudinal edges to the spaced ribs 8 and 9 of the pot. The conductor bar 2 is rigidly secured by suitable rivets 10 and 11 to the attaching plate 1 at one end thereof and preferably projects beyond the ends thereof. As shown. the projecting portion 12 of the bar 2 is flat and has an inclined or off-set end portion 13 carrying a screw 14 constituting a terminal attaching means for the wire 15 leading from the heating unit 7 while the remainder of the bar 2 is channel-shaped and opens toward the attaching plate 1. The projecting portion 16 of said bar 2 carries a fixed electrical Contact button 17. The co-operating conductor har 3 is preferably shorter than the bar 2 but also projects beyond the ends of the attaching plate 1. Preferably this bar 3 extends longitudinally of the channel portion and the attaching plate 1, and is connected to the attaching plate by the rivets 10 and 11. The projecting portion 20 of the bar 3 is flat and has an inclined or off-set end portion 21 carrying a screw 22 constituting a terminal attaching means for the wire 23 leading from the armored cable 24, while the other projecting portion 25 of said bar 3 is flat and has a slightly inclined or off-set end portion carrying an electrical contact button 26 for engagement with the contact button 17 on the conductor bar 2. Preferably a relatively short spacer plate 27 is secured by rivets 10 and 11 between the bars 2 and 3, and a similar spacer plate 28 is secured by the same rivets between the contact bar 3 and the attaching plate 1. Mica strips 29 and 30 are also secured between the conductor bars 2 and 3 and between the spacer plate to insulate the bars from one another and to insulate the said bars from the attaching plate. The cover plate 4 is longitudinally secured at its longitudinal edges to the attaching plate 1 and has a longitudinally extending depressed Vchannel shaped portion 31 that serves as a rigid backer for the conductor bars 2 and 3. The adj usting device 5 preferably comprises a screw 32 that threadedly engages the attaching plate 1 and is adapted to abut and press against the conductor bar 3. Preferably the head 33 of this screw 32 has a laterally proj ecting peripheral flange 34 disposed between an elongated bar 35 and the heads 36 and 37 of two screws 38 and 39 on the bar 35 so as to maintain said screw in proper relation with respect to said bar. Preferably a leaf spring 38 is disposed on the shank of the adjusting screw 32 between the attaching plate 1 and the elongated bar 35 and serves to keep backlash out of the adjusting screw 32.

In use, when the contact buttons 17 and 26 are together, the circuit from the cable 24 to the heating unit 7 is closed, and will remain so until the temperature of the pot 6 reaches a predetermined point, whereupon the conductor bar 3 will move away from the cooperating bar 2 and said contacts 17 and 26 will thereby become separated. Thus the circuit will be opened and the heating unit 7 will be rendered inoperative for heating the pot. In other words, the heat tends to open the contacts against the action of the set screw 39.. This screw, however, serves as a means of adjustment for the initial heating and the cover plate 4 serves as a rigid backer for the conductor bar 2.

While it is believed that from the foregoing description, the nature and advantage of our invention will be readily apparent, we desire to have it understood that we do not limit ourselves to what is herein shown and described and that such changes may be resorted to when desired as fall within the scope of what is claimed.

What we claim as our invention is:

1. A thermostat having a support, an electrical conductor bar having one end secured ""to said support and having a portion of the length thereof substantially channel-shaped in cross section, a second cooperating electrical conductor bar also having one end fixed to-said support and having a portion disposed in the channel-shaped portion aforesecured to said bars, and

said and cooperating electrical contacts on the free ends of said bars.

2. In a thermostat, an attaching plate, a pair of electrical conductor bars carried by "said plate, one of said bars having a channelshaped portion opening toward said plate, the other of said bars having a portion eX- tending longitudinally of and disposed in said channel-shaped portion, and cooperat- `ving electrical contact buttons carried by said bars. Y

3. In a thermostat, a pair of electrical conductor bars, cooperating electrical contact .buttons carried thereby, an attaching plate secured to said bars, and means for adjusting one of said bars including a screw threadedly engaging said plate and having an end engageable with the said bar, a bar sleeved on the shank of said screw, and yieldable means between said bar and attaching plate for preventing back-lash in said screw.

4. In a thermostat, a pair of electrical conductor bars, cooperating electrical contacty buttons carried thereby, an attaching plate means for adjusting one of said bars including an adjustable headed element passing through said plate and engageable with one of' said bars, and

,means for holding said element under tension and in adjusted position including elements associated with the element aforesaid between the head thereof and said attaching plate. v

5. In a thermostat, a pair of electrical conductor bars, cooperating electrical contact buttons carried thereby, an attaching plate secured to said bars, and an adjusting device for one of said bars includingan element passing through said plate, having a head land a lateral flange between the headvand tures.

FRANK KUIIN-- LAURENCE H. THOMAS. 

